Electric glow-discharge vessel



vices.

Patented Apr. 16, 1935 UNITED STATES PATENT OFFICE Erich Koch, llmenau, Germany, asaignor to the firm Rovo A.-G., Zurich, Switzerland No Drawing. Application April 13, 1933, Serial 12 Claims.

This invention relates to the manufacture of electric discharge vessels, especially of luminous discharge tubes and the like producing glow discharges, as used for luminous advertising de- More especially, the invention relates to gas-filled glow-discharge vessels of tubular or another suitable shape in which the inner surface is provided with a layer of a substance or composition which becomes luminous under the action of the electric discharges and varies the tint or tinge of the light emitted in dependency of the kind of the gas or gas mixture with which the tubular or otherwise shaped discharge vessel is filled, that substance or composition being united with the inner surface of the respective vessel or tube, etc., by means of a cementing agent which is volatilizable under the action of heat or in vacuo.

The manufacture of electric discharge tubes according to the present invention proceeds in this way that the inner surface of the discharge vessel, prior to the application of the luminous layer, receives a thin and uniform coating which, besides the substance or component volatilizable by heat. or under vacuo, such as glycerine or the like, contains also boric acid.

In a mode of carrying out this procedure I use for the coating a mixture of about 5 parts of anhydric glycerine and about 1 part of crystalline boric acid, the glycerine being heated, preferably to boiling temperature, and the boricacid being dissolved therein.

Prior to applying this composition to the inner surface of the discharge vessel that surface is thoroughly cleaned and then dried and now the cementing composition is applied to that surface with the aid of a wiping implement in such a manner that said surface receives a thin and uniform coating; thereafter the luminous substance, for instance a luminous sulphide of zinc paint, which should preferably also be employed in purified and dry state, is uniformly distributed over said coating, the discharge vessel being preferably rotated and shaken during this phase; then the vessel is heated to about 330 C. in order to evaporate the liquid component of the cementing composition, thereafter the vessel is exhausted which may also be effected at said temperature, thereupon the vessel is filled with the gas, 1. e. a rare gas, or with a mixture of said gases, may be with an addition of mercury vapor, and finally the vessel is sealed in known manner by melting.

The cementing composition is applied to the inner surface of the discharge vessel preferably In Germany March 6, 1933 by means of an elastic rubber sponge wrapped up in a band of clean mull for several times. For instance the band is wound around two or more times in moist state, at least one time in semidry state, and one time in completely dry state. So the production of a quite uniform and very thin coating of the desired quality is warranted.

Purifying the luminous substance, especially if a sulphide of zinc paint is used, is preferably effected by shaking the substance or paint several 10 times together with distilled water so as to wash it out very thoroughly, the mass being. after every shaking left to itself so as to precipitate the impurities being retained in the water; finally, the thus purified luminous substance or paint is completely dried by means of a current of hot air, preferably in a glass vessel.

By heating the discharge vessel (after the cementing coating and the luminous mass have been applied to the inner surface thereof) to about 330 and by exhausting the vessel also at about this temperature, not only the evaporation of the liquid component of said coating, 1. e. the glycerine, is effected, but also a very firm, shockproof union between the luminous mass and the glass surface is obtained.

The discharge vessels are filled preferably with a mixture of neon, helium, argon, and mercury vapor, obviating, however, an excess of free mercury, as generally used when glow-discharge tubes are filled with the gas. The experiences had with electric discharge tubes containing an excessof free mercury have shown that the inner surface of the tubes is blackened after a longer service whereby the luminous effect of the glowdischarge is considerably impaired. This drawback is completely obviated when said excess of free mercury is prevented.

When the sealing the filled discharge vessels or tubes, for instance tubes representing letters, by melting with the aid of the generally used glass blow lamp it has been found that a certain part of the gas employed for operating that lamp enters into the discharge vessel or tube precipitates therein and penetrates especially also into the luminous layer whereby the luminous effect of this layer is detrimentally affected, in thatan undesired tint or tinge is produced. This undesired effect can be completely obviated by making use of a gasoline lamp for sealing the electric discharge vessels or tubes.

I claim:

l.- The method of manufacturing electric discharge vessels, especially gas-filled electric luminous discharge tubes and the like, having their inner surface provided. by the intermediary of a cementing agent volatilizable under the action of heat or in vacuo, with a layer. of a substance adapted to become luminous under the action of such electric discharges as produce glow light, the tint or tinge of which depends upon the kind of the gas or mixture of gases filling the vessel or tube, said method consisting in using as cementing agent a composition containing boric acid besides the volatilizable substance or substances, and applying a thin and uniform layer of the composition to the inner surface of the discharge vessel or tube prior to applying the luminous substance to the same.

2; The method of manufacturing electric discharge vessels, especially' gas-filled electric luminous discharge tubes and the-like, having their inner surface provided, by the intermediary of a cementing agent volatilizable under the action of heat or in vacuo, with a layer of a substance adapted to become luminous under the action of electric glow-discharges, the tint or tinge of which depends upon the kind of the gas or gas mixture filling the vessel or tube, said method consisting in using as cementing agent a composition consisting of about 5 parts of glycerine and about 1 part of crystalline boric acid, and applying a thin and uniform layer of this composition to the inner surface of the discharge vessel or tube prior to applying the luminous substance to the same.

3. The method of manufacturing electric discharge vessels, especially gas-filled electric luminous discharge tubes and the like, having their inner surface provided, by the intermediary of a cementing agent volatilizable under the action of heat or in vacuo, with a layer of a substance adapted to become luminous under the action of a electric glow discharges, the tint or tinge of which depends upon the kind of the gas or gas mixture filling the vessel or tube, said method consisting, firstly,. in dissolving boric acid in hot anhydric glycerine, secondly, in using this composition as cementing agent, and thirdly, applying a thin and uniform coating of this composition to the inner surface of the discharge vessel or tube prior to applying the luminous substance to the same.

4. The method of manufacturing electric discharge vessels, especially gas-filled electric luminous discharge tubes and the like, having their inner surface provided, by the intermediary of a cementing agent volatilizable under the action of heat or in vacuo, with a layer of a substance adapted to become luminous under the action of electric glow-discharges, the tint or tinge of which depends upon the kind of the gas or gas mixture filling the vessel or tube, said method consisting, firstly, in using as cementing agent or composition containing boric acid besides the volatilizable substance or substances, secondly, in applying a thin and uniform coating of this composition to the inner surface of the discharge vessel or tube prior to applying the luminous substance to the same, and thirdly, in employing as luminous substance a luminous paint containing sulphide of zinc.

5. The method of manufacturing electric discharge vessels, especially gas-filled electric luminous discharge tubes and the like, having their inner surface provided, by the intermediary of a cementing agent volatilizable under the action of heat or in vacuo, with a layer of a substance adapted to become luminous under the action of electric glow-discharges, the tint or tinge of which depends upon the kind of the gas or gas mixture filling the vessel or tube, said method consisting, firstly, in cleaning and drying the inner surface of the discharge vessel or tube, secondly, in using as cementing agent a mixture composed of glycerine and boric acid, thirdly, in applying a thin and uniform coating of this composition to said surface by means of a wiping implement,.fourthly, in applying instantly thereafter the luminous substance uniformly to said coating of the cementing composition, fifthly, in heating the vessel or tube to a temperature at which the glycerine evaporates, sixthly, in exhausting the vessel or tube at practically the same temperature, seventhly, in filling it with a rare gasor mixture of such gases, and eighthly, in sealing it by melting.

6. The method of manufacturing electric discharge vessels, especially gas-fllled electric luminous discharge tubes and the like, having their inner surface provided, by the intermediary of a cementing agent volatilizable under the action of heat or in vacuo, with a layer of a substance adapted to become luminous under the action of electric glow-discharges, the tint or tinge of whichdepends upon the kind of the gas or gas mixture filling the vessel or tube, said method consisting in cleaning and drying the inner surface of the discharge vessel or tube, using as cementing agent a mixture composed of anhydric glycerine and crystalline boric acid, applying a thin and uniform coating of this composition to said surface by means of a, wiping implement, applying instantly thereafter the luminous substance uniformly to said coating of the cementing composition and turning and shaking the vessel or tube at the same time so as to distribute said composition uniformly, heating the vessel or tube to a temperature at which the glycerine evaporates, exhausting the vessel or tube at practically the same temperature, filling it with a rare gas or a mixture of such gases, and sealing 7. The method of manufacturing electric discharge vessels, especially gas-filled electric luminous discharge tubes and the like, having their inner surface provided, by the intermediary of a cementing agent volatilizable in heat or under vacuo, with a layer of a substance adapted to become luminous under the action of electric glow-discharges, the tint or tinge of which depends upon the kind of the gas filling the vessel or tube, said method comprising, in addition to the phases stated in claim 6, an addition of mer- -cury vapor to the rare gas or mixture of gases filled into the exhausted discharge vessel or tube.

8. The method of manufacturing electric discharge vessels, especially gas-filled electric luminous discharge tubes and the like, having their inner surface provided, by the intermediary of a cementing agent volatilizable by heat or under vacuo, with a layer of a substance adapted to become luminous under the action of electric glow-discharges, the tint or tinge of which depends upon the kind of the gas filling the vessel or tube, said method comprising, in addition to the phases stated in claim 1, purifying the luminous substance prior to applying it to the coating of the cementing agent.

9. The method of manufacturing electric discharge vessels, especially gas-filled electric luminous discharge tubes and the like having their inner surface provided, by the intermediary of a cementing agent volatilizable by heat or under vacuo, with a layer of a substance adapted to become Iuminous under the action 01 electric'glowdischarges, the tint or tinge of which depends upon the kind of the gas or gas mixture filling the vessel or tube, said method comprising, in addition to the phases stated in claim 1, washing the luminous substance several times in distilled water, letting it precipitate therein, and drying it by means of a current of hot air, prior to applying it to the coating of the cementing agent.

10. The method of manufacturing electric discharge vessels, especially gas-filled electric luminous discharge tubes or the like, having their inner surface provided, by the intermediary of a cementing agent volatilizable in heat or under vacuo, with a layer of a substance adapted to become luminous under the action of electric glow-discharges, the tint ortinge of which decharge vessels. e pecially gas-filled electric luminous discharge tubes or the like having their inner surface provided with a layer of a substance becoming luminous under the action of the electric discharge, the tint or tinge of which depends upon the nature of said substance and of the kind of the gas or mixture of gases filling the vessel or tube, said method comprising, in addition to the phases stated in claim 1, sealing the vessel or tube by means of a gasoline lamp.

12. 'Ilhe method of manufacturing electric discharge tubes, especially gas-filled luminous discharge tubes having their inner surface covered with a layer of a substance becoming luminous under the action of the electric discharges, the tint or tinge of which depends upon the kind of the rare gas or mixture of such gases filling the tube, said method comprising, in addition to the phases stated in claim 1, sealing the tube by melting its open end by means or a gasoline lamp after said layer has been applied and the tube has been exhausted.

ERICH KOCH. 

